Does insular cortex lesion cause tinnitus in rats?

Objectives: Tinnitus is defined as ringing of the ears that is experienced when there is no external sound source, and is an auditory phantom sensation. The insula as a multimodal cortex has been shown to be involved in the processing of auditory stimuli rather than other sensory and motor processing and reported to correlate with some aspects of tinnitus. However, its exact role is not clear. The present study aimed to investigate the effect of excitotoxic lesions limited to the insular cortex on the ability to detect a gap in background noise. Materials and Methods: Gap detection test and prepulse inhibition, two objective measurements of auditory startle response, were measured, in 33 male Wistar rats, before and up to four weeks after insular lesion in three experimental groups (sham, control, and lesion). Results: The ability to detect the gap interposed between 60 db background noise was impaired at weeks 2, 3, and 4 following insular lesion, while prepulse inhibition remained intact up to four weeks after surgery. Conclusion: These findings indicated that excitotoxic lesions of the insular cortex may produce a tinnitus-like phenomenon in rats while sparing the hearing sensitivity; suggesting that the insular cortex may have a role in the development of tinnitus.

The effect of insular cortex lesion on hyperacusis-like behavior in rats.

Background and objectives: Hyperacusis is hypersensitivity and extreme response to the intensity of sound that is tolerable in normal subjects. The mechanisms underlying hyperacusis has not been well understood, specially the role of insular cortex. The aim of this study is to investigate the role of insular cortex in hyperacusis like behavior. Material and methods: The number of 33 male wistar rats weighting 170-250 gr were allocated randomly in three groups; control, sham, and insular lesion. Auditory startle responses (ASR) to different intensities of stimuli (70, 80, 90, 100, and110 dB without background noise as well as 110 dB in the presence of 70, 80 dB background noise) were measured before and up to four weeks after intervention. Results: Data analyses showed an increase in ASR to 100 dB stimulus without background noise one week after insular lesion, and increased responses to other intensities two weeks after lesion. Furthermore, there was a decrease in ASR to 110 dB stimulus with 80 dB background noise two weeks after insular lesion. However, no significant difference was observed in 70 dB background noise. The changes in ASR lasts at least four weeks.Conclusion: The findings indicated that there was an increase in ASR in the absence of background noise following cortical excititoxic lesion limited to insular cortex, while there was a decrease in responses in the presence of background noise which suggests possible increased sensitivity to sound loudness as a hyperacusis-like phenomenon. The study showed a significant relationship between insular cortex lesion and ASR in rats.

Does 5, 7-Dihydroxytryptamine injection into nucleus accumbens cause hyperacusis?

Hyperacusis may be defined as diminishing tolerance to moderate and high intensity sounds in people with normal hearing sensitivity. Serotonin plays a critical role in some of auditory tasks including startle reflex and prepulse inhibition. Serotonin deficiency can cause some diseases which can coincide with hyperacusis. The aim of the present study was to investigate the probable influence of serotonergic depletion in nucleus accumbens (NAcc) on the startle reflex. The startle reflexes were examined in Wistar rats (n: 48) in different intensities with and without the background noise. The amplitude of startle reflex significantly increased in NAcc-injected rats without background noise, while this difference disappeared in the presence of background noise in all intensities. These data proposed that the injection of 5, 7-Dihydroxytryptamine (5, 7-DHT) into nucleus accumbens will cause hyperacusis-like behavior, and strengthens the possibility of the role of serotonin and nucleus accumbens in hyperacusis.

Comparison of aural rehabilitation outcomes in presence and absence of back ground noise in hearing impaired children with and without attention deficit hyperactivity disorder (ADHD).

OBJECTIVE: We sought to understand the extend of improvement in seven major skills to determine the best rehabilitation approach in hearing impaired young children with and without attention deficit and hyperactivity disorder (ADHD). METHODS: Newsha developmental scale was assessed in 40 hearing impaired children with and without ADHD in two conditions, in which seven major skills (hearing, speech, receptive language, expressive language, cognition, social communication, and motor skills) were evaluated. Two separate analyses were conducted, each after six months of rehabilitation. The first six months rehabilitation was done by controlling background noise level, while the other six months rehabilitation was performed with background multi talker babble noise, and ADHD and non ADHD children performance were compared. RESULTS: After the first six months of rehabilitation there were no significant difference in improvement in any of the major skills except for motor and cognition skills between hearing impaired ADHD and non ADHD children. After the second six months of rehabilitation the extend of improvement was equal in both groups. CONCLUSION: The equal improvement of hearing impaired ADHD and non- Children with ADHD support the benefits of rehabilitation program in both groups. In addition, it seems background multi talker babble noise can facilitate the process of rehabilitation in ADHD group. As a result, it is important to understand the specific needs of hearing impaired children with ADHD in rehabilitation program to provide the best services and increase the chance for success.

Translation, validity, and reliability of a persian version of the iowa tinnitus handicap questionnaire.

INTRODUCTION: Tinnitus is a common otologic symptom that can seriously affect a patient's quality of life. The purpose of the present study was to translate and validate the Iowa Tinnitus Handicap Questionnaire (THQ) into the Persian language, and to make it applicable as a tool for determining the effects of tinnitus on a patient's life. MATERIALS AND METHODS: The main version of the THQ was translated into the Persian language. The agreed Persian version was administered to 150 tinnitus patients. The validity of the Persian THQ was evaluated and internal reliability was confirmed using Cronbach's α-coefficient. Finally, the effect of independent variables such as age, mean patient threshold, gender, and duration of tinnitus were considered in order to determine the psychometric properties of tinnitus. RESULTS: After an exact translation process, the Persian THQ was found to exhibit face validity. In terms of content validity, content validity index in total questionnaire was 0.93. Further, in structural validity measurements, intermediate correlation with annoyance from tinnitus (r=0.49), low correlation with duration of tinnitus (r=0.34) and high correlation with the Tinnitus Handicap Inventory (THI) questionnaire (r=0.84) were demonstrated. Additionally, a negligible effect of gender and age was noted on degree of tinnitus handicap (P= 0.754, P= 0.573, respectively). In the internal reliability assessment for Factors 1, 2, 3, and the whole questionnaire, Cronbach`s α-coefficient was 0.95, 0.92, 0.25 and 0.88, respectively. CONCLUSION: The Persian version of the Iowa THQ demonstrates high validity and reliability and can be used for the determination of tinnitus handicap and for following-up in the intervention process in Persian tinnitus patients.

Evaluation of distortion and transient evoked otoacoustic emission in tinnitus patients with normal hearing.

INTRODUCTION: Tinnitus is a perception of sound without external source. The exact etiology of tinnitus is not fully understood, although some researchers believe that the condition usually starts in the cochlea. The aim of this study was to determine the potential contribution of outer hair cell dysfunction to chronic tinnitus, by application of Distortion-Product Evoked Otoacoustic Emission (DPOAE) and Transient Evoked Otoacoustic Emission (TEOAE) and also to determine the relationship between tinnitus loudness and the amplitude of these two potentials. MATERIALS AND METHODS: This study was conducted on 20 tinnitus patients aged 20-45 years and 20 age- and gender-matched control subjects. DPOAE and TEOAE were performed on each subject. RESULTS: The difference in the amplitudes of TEOAE between the two groups was not significantly different (P=0.08), but the amplitude of DPOAE in patients with tinnitus was significantly lower than the corresponding value in the control subjects (P=0.01). There was no correlation between tinnitus loudness and the amplitudes of neither DPOAE nor TEOAE. CONCLUSION: Abnormal findings in the DPOAE of tinnitus sufferers suggest some form of cochlear dysfunction in these patients. As there was no correlation between the amplitude of the recorded potentials and tinnitus loudness, factors other than cochlear dysfunction may also influence the loudness of tinnitus.